1. Field of the Invention
The invention relates to a fabric printer ribbon, which is impregnated with a transfer medium comprised of a vehicle liquid and a coloring agent dispersed in the vehicle. The ribbon may further contain additives which improve its properties.
2. Discussion of the Background
Known printer ribbons, which are employed as ink ribbons or similar fabric printing media in typewriters, adding and calculating machines, punch card machines, computers, printers, addressing machines, and the like, contain ordinary coloring agents in the form of dyes and/or pigments. Current terminology used in the art will be followed rigorously. Accordingly, the term "coloring agent" comprises both dyes and pigments, with pigments being insoluble and dyes being soluble in the relevant solvents and/or binders. The dyes concerned are the classical organic and inorganic dyes. Such dyes are described in detail in various editions of "Coulour Index", 3rd Ed., 1971, pub. Society of Dyes and Colorists, Bradford, Yorkshire, England, and American Association of Textile Chemists and Colorists, Research Triangle Park, N.C., U.S.A.; and in "Schulzes Farbstofftabellen", 7th Ed., 1931, pub. Akademische Verlagsgesellschaft m.b.H., Leipzig.
Printer ribbon inks for monochrome ribbons are comprised chiefly of triturations of fat-soluble dyes or of lakes. In the case of document inks, triturations may also comprise carbon black, and the inks may further contain oils, fats, and fatty acids. Dyes for multicolored ribbons genrally have a somewhat different basic composition. For example, they should not contain oleic acid, which promotes diffusion into other color zones. The printer ribbon inks are generally applied to the ribbons after the printing process by means of ink ribbon impregnating machines. By this technique, the coloring of the colored ribbon occurs as the latter passes over a steel cylinder. A rubberized roll bearing the printer ribbon inks is pressed against the ribbon on one face of the ribbon, to apply the colored ink, and then the back side of the ribbon is inked on a second steel cylinder. By controlling the amount of ink and the pressure of the applied rubber rollers, or by inking the inked ribbon a number of times, any required ink intensity can be readily achieved, without damage to the fabric of the ribbon. Two-color and multicolor inked ribbons are produced by this technique. The inked ribbons are then wound up on spooling machines, where the ribbons are wound onto, e.g., typewriter ribbon spools.
The coloring agents described above have the advantage of providing durable inked printing. However, due to their chemical characteristics, there is no chemical correction means which can be used with them which does not damage the paper. This drawback has not yielded to research on suitable correction agents, despite many years of effort. Surprisingly, it has been discovered in connection with the present invention that by the choice of special coloring agents which can be gently bleached from the described paper, one can devise an advantageous fabric printer ribbon without detriment to the other desirable characteristics of commercial products currently in use. The known bleachable aqueous inks, i.e., extinguishable printer ribbon inks, are not suitable for this purpose. The extinction mechanism with such inks takes place solely in the aqueous phase.